tree 018e5089fe162ee22152bd3c1c0f9a8522397ea5
parent 2cf8429a95212314f9b1237e9c338ee3a46ab1ed
author Sho SHIMIZU <sshimizu@us.fujitsu.com> 1471043284 -0700
committer Sho SHIMIZU <sshimizu@us.fujitsu.com> 1471045851 -0700

Use JDK's Optional instead of Guava's Optional

Change-Id: Ia37b2977ede215363374e292b5565f007f1d6483